Conventionally, a buildup wiring board is manufactured, with a network-formed print wiring board as the inner layer core material, by laminating a copper foil for a outer layer circuit on the inner layer core material via a resin-impregnated base material or in a form of a resin-added carrier foil, and thereafter forming an interlayer connection and network.
Moreover, the foregoing process is repeated to build up the outer layer circuits according to the required number of layers.
Generally, upon pressing a copper foil with a pressing or laminating machine, if foreign matter such as copper scrape or prepreg resin powder generated when cutting the copper foil adheres to the shining surface (S surface) of the copper foil, there is a problem in that such shining surface will become scratched, or foreign matter will adhere thereto. Moreover, even after lamination, there are cases where the shining surfaces would scrape against each other and become scratched when removing the copper-clad laminate from the device or overlaying such copper-clad laminates.
In recent years, the circuit width is becoming significantly small due to the miniaturization demands of electronics, and, pursuant thereto, the thickness of copper foil used in the copper-clad laminate has become less than 18 μm in consideration of the demands for copper foil with reduced thickness.
Nevertheless, the handling extremely aggravates when the thickness of the copper foil is reduced to less than 18 μm. In addition to the aforementioned pressing or laminating process, there is a problem in that the copper foil may become scratched during the ordinary cutting packaging or transportation thereof, and the shining surface of the copper foil in particular may be affected by the increased contamination of foreign matter or generation of wrinkles and creases.
As described above, when scratches, wrinkles or creases occur, particularly on the shining surface side, it will cause the disconnection and short circuit of circuits, and there is a significant problem in that this will lead to defects in the print circuit substrate and electronic equipment.
Several proposals have been made for preventing scratches, wrinkles and creases on the copper foil surface described above and improving the handling thereof. One example of such a proposal is to use a carrier of aluminum foil or copper foil and to adhere such carrier to the copper foil with an adhesive agent.
This will reinforce the foregoing ultra-thin copper foil, improve the handling of such copper foil, protect the copper foil surface during cutting; particularly the shining surface (S surface) of the copper foil, prevent contamination such as resin powder from adhering to such surface, and prevent scratches and dimples caused by foreign matter. Here, those with an aluminum carrier are generally referred to as CA (Copper Aluminum) foil.
Usually, at the subsequent step, this type of CA foil is laminated with a resin-impregnated base material, heated/pressed with a pressing device, and thereafter made into a copper-clad laminate used in a print circuit substrate. Ultimately, the foregoing aluminum carrier is peeled, and completes its role as the carrier and contaminant protective layer.
When employing the resin-added copper foil to the foregoing carrier-added copper foil, resin power would arise from the resin layer end face upon performing slit processing to the resin-added copper foil, or from the resin layer end face upon cutting after applying the carrier, and there is a problem in that the product or process would become contaminated.
Similar problems would arise when employing a functional material layer to which ferroelectrics are dispersed instead of the foregoing resin layer. Further, when forming a layer comprising the functions of an insulating layer and dielectric layer within the same substrate, buildup will be necessary for each individual layer, and problems of complicated procedures and increased costs are expected due to the increased number of substrate layers.